U.S. patent number 5,607,633 [Application Number 08/502,167] was granted by the patent office on 1997-03-04 for co-adhesive system for bonding wood, fibers, or agriculture based composite materials.
This patent grant is currently assigned to Archer Daniels Midland Company. Invention is credited to Kenneth D. Roos, Ronald T. Sleeter.
United States Patent |
5,607,633 |
Sleeter , et al. |
March 4, 1997 |
Co-adhesive system for bonding wood, fibers, or agriculture based
composite materials
Abstract
The invention provides an adhesive system comprising a blend of
resin and a co-adhesive conjugated triglyceride, which is
especially well suited to bonding composite panels such as oriented
strand board, particle board, plywood, MDF, hardboard, and similar
panels. The resin is a fast acting bonding material which forms a
mat of fibers into a self sustaining panel within a time limit
during which a press may be economically utilized. The triglyceride
acts slower so that, after the panel is formed, there is enough
time to penetrate the fibers to a depth that results in a superior
bonding.
Inventors: |
Sleeter; Ronald T. (Decatur,
IL), Roos; Kenneth D. (St. Peter, MN) |
Assignee: |
Archer Daniels Midland Company
(Decatur, IL)
|
Family
ID: |
23996647 |
Appl.
No.: |
08/502,167 |
Filed: |
July 13, 1995 |
Current U.S.
Class: |
264/115;
264/109 |
Current CPC
Class: |
C08L
97/02 (20130101); C08L 97/02 (20130101); C08L
2666/02 (20130101) |
Current International
Class: |
C08L
97/02 (20060101); C08L 97/00 (20060101); B29C
067/00 () |
Field of
Search: |
;264/115,109 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Theisen; Mary Lynn
Attorney, Agent or Firm: Laff, Whitesel, Conte & Saret,
Ltd.
Claims
The claimed invention is:
1. A co-adhesive bonding process for fibrous material, said process
comprising:
blending an adhesive of a fast acting bonding material in
combination with a conjugated triglyceride oil;
combining said blend with fibrous materials;
said conjugated triglyceride oil soaking into and penetrating said
fibers; and
subjecting said combined fibrous material and said blend to heat
and pressure for polymerizing said fast acting bonding material and
bonding said fibrous material into a composite panel.
2. The bonding process of claim 1 wherein said fast acting bonding
material is taken from a group consisting of Urea-Formaldehyde,
Phenol-Formaldehyde, Melamine-Urea-Formaldehyde, Polyvinyl Acetate,
Isocyanate, Resorcinol-Phenol-Formaldehyde, Protein,
Tannin-Formaldehyde, and Sulfite-Liquor.
3. The bonding process of either claim 1 or claim 2 wherein said
conjugated triglyceride is taken from a group consisting of linseed
oil, soybean oil, tung oil, and fish oil.
4. The bonding process of either claim 1 or claim 2 wherein said
conjugated triglyceride is an oil containing a material taken from
a group consisting of linolenic acid, linoleic acid and
eicosapentanoic acid.
5. The bonding process of either claim 1 or claim 2 wherein said
triglyceride is an oil having conjugatable double bonds.
6. The bonding process of claim 5 wherein said triglyceride is
conjugated by a catalyst taken from the group consisting of
ruthenium, SO.sub.2, amine hydroiodides, primary alcohols, alkali,
anthraquinone, and nickel/carbon.
7. The bonding process of claim 5 wherein said triglyceride is
taken from a group consisting of a very hard hydrogenated fat, and
a hydrocarbon wax having a very high melting point.
8. The bonding system of claim 1 or claim 2 where a mixture of wood
chips and said adhesive blend are mixed in a blender and pressed at
a pressure and heat determined by parameters of said composite
panel.
9. A method of making a composite panel from fibrous material
comprising the steps of:
reducing the fibrous material to fibrous strands;
preparing an adhesive blend of resin and conjugated triglyceride
bonding agents;
mixing said fibrous strands and said adhesive blend of bonding
agents;
orienting said fibrous strands into a mat comprising a stack of
layers, the oriented fibrous strands in each of said layers lying
at approximately right angles with respect to the orientation of
the fibrous strands in the neighboring layers, and
pressing the mat under a pressure in the range of about 525-100 PSI
for a time period in the order of about 1-5.5 minutes, at a
temperature of about 380.degree. F.
10. The method of claim 9 and the added step of selecting said
resin from a group consisting of Urea-Formaldehyde,
Phenol-Formaldehyde, Melamine-Urea-Formaldehyde, Polyvinyl Acetate,
Isocyanate, Resorcinol-Phenol-Formaldehyde, Protein,
Tannin-Formaldehyde, and Sulfite-Liquor.
11. The method of claim 9 and the added step of selecting said
conjugated triglyceride from a group consisting of linseed oil,
soybean oil, tung oil, and fish oil.
12. The method of claim 9 and the added step of conjugating said
triglyceride by use of a catalyst taken from a group consisting of
ruthenium, SO.sub.2, amine hydroiodides, primary alcohols, alkali,
anthraquinone, and nickel/carbon.
13. The method of claim 9 wherein said triglyceride is taken from a
group consisting of a very hard hydrogenated fat, and a hydrocarbon
wax having a very high melting point.
14. The method of claim 9 and the added steps of applying said
adhesive blend to wood chips through a coil spinning disc atomizer,
said disc spinning at approximately 12000 RPM, blending the blend
and the chips in a blender at approximately 24 RPM, and pressing
the resulting wood chips at a pressure in the range of about
525-100 PSI for a period of time in the range of about 1-5 minutes,
said pressing being at a temperature of about 380.degree. F., said
pressure being at about 525 PSI starting pressure, then at about
175 PSI for about 1.5 minutes, then at about 100 PSI for about 4.5
minutes, then at about 0 PSI for about 5.0 minutes, with an open
press at about 5.5 minutes.
15. A method of making a panel from fibrous wood material
comprising the steps of:
preparing an adhesive blend of resin and conjugated triglyceride
bonding agents by reacting methylene interrupted organic compounds,
in the absence of oxygen and in the presence of an acid, with a
ruthenium compound chosen from the group consisting of
organo-ruthenium complexes, soluble ruthenium metal, ruthenium
salts, and ruthenium covalent compounds;
mixing said fibrous wood material and said adhesive blend of
bonding agents;
orienting said fibrous wood material into a mat comprising a stack
of the fibrous wood material; and
pressing the mat under a pressure in the range of about 525-100 PSI
for a time period in the order of about 1-5.5 minutes, at a
temperature of about 380.degree. F.
16. A method of making a wood panel comprising the steps of:
reducing wood to fibrous material;
modifying a methylene interrupt in a triglyceride prepared by
reacting the triglyceride in the presence of an acid, with a
ruthenium compound chosen from the group consisting of
organoruthenium complexes, soluble ruthenium metal, ruthenium
salts, and ruthenium covalent compounds, said triglyceride being
taken from a group consisting of linseed, fish, soybean, tall,
tung, corn, sunflower, castor, and oiticica, a very hard
hydrogenated fat, and a hydrocarbon wax having a very high melting
point;
preparing an adhesive blend of resin and said modified
triglyceride;
mixing said fibrous wood material and said adhesive blend;
orienting said fibrous wood material into a mat comprising a stack
of the fibrous wood material; and
pressing the mat under a heat and pressure.
17. The method of claim 16 in which the triglyceride is a common
vegetable oil.
18. The method of claim 17 in which the common vegetable oil is
linseed oil.
19. The method of claim 17 in which the common vegetable oil is
soybean oil.
20. The method of claim 16 in which a conventional antioxidant is
included in the modifying step.
Description
This invention relates to an adhesive system especially--but not
exclusively--for bonding various wood, wood chip, fiber, and
agriculture based composite based materials and more
particularly--but again not exclusively--to means for and methods
of making a new and improved particle board, plywood, oriented
strand board, medium density fiberboard, hardboard, structural
strand lumber, or the like.
Reference is made to a companion patent application Ser. No.
08/472,919, filed Jun. 7, 1995, which describes the co-adhesive
system, per se, which is used as described herein. This co-adhesive
system could be used in conjunction with PF, UF, melamine, aromatic
isocyanate resins, or a combination of these resins. The inventive
system enables a production mill to reduce overall resin cost,
reduce overall mill VOC emissions, and diminish maintenance on
operations equipment. The co-adhesive can also be blended with a
natural wax to act as a wax/sizing agent in order to replace the
petroleum waxes used heretofore, i.e., slack wax and or petroleum
based emulsion waxes used in the manufacturing processes.
"Drying oils" are triglycerides which have the ability to dry or
polymerize. Text material on drying oils is found in Bailey's Fats
and Oils, Ch. 10. Some examples of drying oils are: linseed, fish,
soybean, tall, tung, castor and oiticica. Drying oils are composed
of fatty acids which have a preponderance of two or three double
bonds. The drying ability of these oils is related to their Iodine
Value ("IV"), which is a quantitative measure of the number of
double bonds that they contain. Oils in the range of 195-170 IV are
relatively fast-drying. Oils in the range of 140-120 IV are
semi-drying, and oils with IV's under 120 are non-drying.
"Drying oils" include conjugated oils. The term "conjugation" is
used herein to describe triglycerides which have double bonds on
adjacent carbon atoms.
For natural oils containing more than one carbon to carbon double
bond, the double bonds are generally separated by a methylene
group, commonly referred to as being "methylene interrupted". These
fats and oils have nutritional benefits; however, the methylene
interruption limits their use in industrial polymerization
applications, where they could find use as coatings, adhesives and
the like. For these fats and oils to be so used industrially, they
need to polymerize rapidly. For this to occur, it is advantageous
to have the double bonds adjacent to one another or "conjugated"
(i.e., the methylene interrupt is shifted or relocated).
A simple explanation of this methylene interrupt shift is
illustrated by the following example showing only carbon atoms:
The carbon chain on the left is methylene interrupted between the
two carbon atoms having double bonds. The carbon chain on the right
is conjugated by shifting the methylene group to the end of the
chain of carbon atoms.
For these vegetable oils to be useful industrially, they need to be
made to polymerize rapidly. This can be accomplished by conjugating
the double bonds to produce rapidly polymerizing oils. Over the
years, many methods have been developed to produce conjugated oils
by shifting the methylene interruption between the double bonds.
Unfortunately, only limited commercial amounts of such modified
vegetable oils have been produced using these methods due to their
expense and other limitations.
Plant life gives off volatile organic compounds ("VOC") which are
atmospheric pollutants. In the wild, VOC's tend to be unimportant
and it would be very rare, if at all, that natural VOC's would
create a problem. However, in the manufacture of certain products
based on plant life, there can be a concentration of VOC's which
become a serious pollutant. Therefore, in any product such as this
invention a limitation upon the output of the VOC's becomes very
important. Federal, state and local regulations severely limit the
release of VOC's; see, for example, the EPA Clean Air Act.
Wood is one of the world's most significant renewable resources.
However, since the world's supply of large diameter trees for
producing lumber and plywood products is decreasing, modern
technology is trying to extend the dwindling forest resources. As a
result, smaller diameter trees and more species types are being
used. Hence, the production of plywood and other wood composites,
including particle board, using adhesives as binder, has increased
substantially during the last 50 years.
By way of comparison, plywood manufacturing recovers only about
60-70% of the tree stem. Particle board and "oriented strand board"
or simply "OSB", can satisfactorily utilize, perhaps, in the order
of 90% of the same tree stem. The particle boards are wooden strand
panels bonded with resol resins, urea formaldehyde or isocyanate,
and polymeric methylene diphenyl diisocyanates. The remainder of
the specification will focus on oriented strand boards "OSB", by
way of example; however, this concentration on OSB is for
convenience of this description and does not limit the invention
thereto. The invention is applicable to at least plywood, particle
board, OSB and all similar boards.
In order to make OSB, bark is first stripped from logs, and then,
the debarked logs are cut into suitable lengths and fed into a
flaker. There, they are reduced into thin flakes which are
fractured to produce narrow, thin strands of wood. These wood
strands are dried to reduce their moisture content from roughly 50
percent to about 5 percent of the total mass.
Next, the dried strands are blended with a suitable petroleum based
"slack" wax or emulsion and a liquid or dry resin which is a glue
that binds the strands together later in the manufacturing process.
The petroleum based wax helps repel water in the finished flake
board. The strands are then formed into mats with the strands
oriented so that the strands of one layer lie crosswise over the
strands of the next neighboring layer. The result is a five-layer,
for example, mat of cross-oriented strands which is several inches
thick. Thereafter, the strand-laden sheets are loaded into a press
where heat and pressure are applied simultaneously in order to
compress the mat to desired thickness and activate the resin,
thereby bonding the strands into particle board panels.
When a composite board, such as a particle or OSB board, is made,
the wood fibers and adhesive material are placed in a press which
applies a pressure for several minutes. The total time in the press
varies with the parameters of the mat and with the resin
technologies that are used. The thicker the mat the longer the
press time. The adhesive bonds the wood particles together so that
they become a completed self-sustaining panel by the time that the
press opens.
It is thought that the bonding time has to do with how long it
takes for the adhesive to polymerize, especially under the pressure
and temperature conditions prevailing in the closed press. However,
it is also thought that this need for rapid bonding is the cause of
some of the problems with particle board such as edge swelling,
delamination, patches tearing away, and the like.
One of the problems with particle boards is that patches of the
aggregated fibrous material may be torn from the surface of the
board, edges of the panel may delaminate, or swelling may occur,
especially if the particle board is mechanically stressed or
exposed to hostile environments. In general, this tendency for
patches of particle board to tear out or otherwise separate is
addressed by this invention.
More particularly, the invention uses a drying oil or catalytic
bonding material, especially as a co-adhesive for bonding and
securing the aggregation of wood chips, fibers, or other
agriculture based composite materials into the composite panel, in
combination with a conventional adhesive. One example of such a
drying oil or catalytic bonding material is found in European
Patent Application No. 0 040 577, dated May 14, 1981, opened to the
public Nov. 25, 1981, Georges Cecchi and Eugene Ucciani, inventors.
However, it has been found that the ruthenium on carbon, as
practiced by Cecchi and Ucciani in the European Patent Application
No. 0 040 577, was not capable of reuse as claimed. It is critical
for a process of this nature to be capable of numerous reuses due
to the expense of the catalyst. Catalyst activity for used catalyst
of this patent is reduced by a factor of one-half for every reuse,
when used for conjugation of linseed oil. Typical conversions start
at 85% conjugation for the first reaction, about 40% conjugation
for the second reaction with the catalyst used once, and about 20%
conjugation for the third reaction with the catalyst used twice.
Therefore, for practical commercial products, the Cecchi-Ucciani
procedure leads to a prohibitively high cost to make conjugated
oil, primarily due to the loss of catalyst activity. Thus, the use
of ruthenium on carbon alone is not a viable process.
Before adopting a new bonding material, at least four major factors
should be considered:
1) ease of formulation and application of the bonding material,
2) effect on the physical properties of the board,
3) effect on the environment and human health, and
4) the relative costs of alternative materials.
Linseed oil is the first choice drying oil for use in the invention
due to its high levels of unsaturation (IV=155-205), especially of
linolenic acid which generally exceeds 55% by weight. Linseed has
well-known agronomic properties and has been grown in the past in
large quantities. Soybean oil and safflower oil are two other
candidates. However, they are generally considered less desirable
because they have less total unsaturation with most of the
unsaturated fatty acids in these oils being linoleic (IV=120-141
and 145 respectively).
Prior methods for the conjugation of double bonds in drying oil
yield low conversions requiring long reaction times at high
temperatures. This low yield favors subsequent polymerization of
the conjugated products being formed thereby additionally lowering
the yield. The conjugation of the oil proceeds through an optimum
yield of conversion at which point polymerization outpaces
conjugation and the amount of conjugated oil actually decreases as
the reaction proceeds. This ultimately produces an oil of such high
viscosity as to render it useless for many applications.
In general, the cost of the inventive product made with the
inventive co-adhesives is significantly less than the cost of the
material which it replaces, and thus providing a lower overall cost
of manufacturing without sacrificing the quality and strength of
the composite panel. Also, the co-adhesives may be upgraded to
produce products with specifications which cannot otherwise be
produced without resorting to adhesives of much greater expense. As
well, the inventive co-adhesives have much reduced VOC's.
Adhesives currently used by manufacturers of various wood
composition based panels include urea-, phenol-, melamie-urea and
melamine-formaldehyde and polymeric isocyanate ("UF", "PF", "MUF",
"MF", and "PMDI"). However, manufacturers of composite panels
continue to search for supplements to or replacements for adhesives
presently used, especially those which are based on urea- and
phenol-formaldehyde adhesives, because of environmental and health
concerns. Primarily the effort is to reduce or eliminate the
emitted amount of free formaldehyde, especially the emissions
resulting from consolidating mats of resin-coated particles under
heat and pressure. These efforts are primarily directed to altering
resin chemistry or adopting resin components or new adhesives, such
as isocyanates that do not emit formaldehyde.
Isocyanates are one of the adhesives which are currently used as an
alternative to the environmentally unfriendly adhesives. However,
isocyanates present disadvantages that must be also considered.
Even though somewhat better than prior adhesives, the isocyanates
are not entirely free of health risks. The isocyanates can react
with moisture on the skin or with moisture in the lungs if inhaled
as atomized isocyanate or isocyanate-coated wood dust. Also,
isocyanates can cause manufacturing problems since they can bond to
metals (i.e., metal plates and presses) and can have a considerably
shorter open time on the stands than UF or PF. Isocyanates may be
more expensive than other conventional adhesives.
More information on suitable adhesives can be found in articles in
the publication "Adhesives Age" for May 1981 (pages 41-44) and
October 1992 (pages 22-25).
Accordingly, an object of this invention is to provide new and
improved adhesive materials having a widespread use,
especially--but not exclusively--as adhesives used to manufacture
OSB, particle board, plywood, or the like. Here, an object is to
provide drying oils or bonding agents which may be used in
conjunction with other adhesives in order to make a bonding system
superior to either resin or a drying oil taken alone. In
particular, an object is to provide composite panels, such as OSB,
particle boards, plywood or the like, which have an increased inner
bond strength and are less prone to tearing, swelling or
delaminating.
Another object of the invention is to provide new uses for
agriculture products, especially for residual agriculture materials
which may remain after more valuable elements (such as food
products) have been removed therefrom.
Accordingly, in keeping with an aspect of the invention, a first
co-adhesive system has an amount of conventional adhesive that is
used to quickly form the fibrous mat into a bonded board or panel.
A second co-adhesive is an amount of conjugated triglyceride or
drying oils which is added to penetrate the wood fibers of the
bonded board or panel over an extended drying time, thereby
enhancing the bonding strength as compared to the strength of the
adhesive system using only a resin alone.
The inventive system is based on a conjugated triglyceride, such as
a preferred modified linseed oil containing amounts of linolenic
acid, which are a portion in the order of 50% or higher of the
total linseed oil. Other unsaturated triglycerides containing high
amounts of linoleic acid may also be utilized, but are not
necessarily preferred, such as: soybean oil, China wood oil or tung
oil, tall oil, castor oil, oiticica oil, various fish oils and the
like.
It has been discovered that most organo-ruthenium complexes,
ruthenium salts and, to a limited degree, ruthenium covalent
compounds and ruthenium salts in which ruthenium is in any of its
several valence or oxidation states, catalyze the conjugation of
methylene interrupted double bonds in common vegetable oils. Most
compounds of ruthenium which can be solubilized into the substrate
(oils with high Iodine Values composed of methylene interrupted
double bonds) are or form active homogeneous catalysts to conjugate
double bonds. Indeed, organic compounds in general which have
methylene interrupted double bonds can be conjugated with the
process of this invention.
It has been found that the successful use of these forms of
ruthenium depends upon the presence of an acid during the reaction.
The preferred acid is formic acid. Some other acids such as organic
acids (e.g., acetic, benzoic, oxalic) or HCl (in gaseous form) and
also some low molecular weight alcohols (e.g., methanol, ethanol
and isopropyl alcohol) work with ruthenium, but to a much lesser
degree.
Also, combinations of these acids, such as formic acid and HCl
(gaseous), may be used. In addition, surprisingly low levels of
ruthenium of the order of 10-20 ppm can achieve in excess of 80%
conversion to conjugation. These catalysts can be used at any
level, although the conversion of methylene interrupted double
bonds to conjugated double bonds decreases in efficiency as lower
and lower levels of catalyst are used based on ruthenium content.
Thus, the level of ruthenium as metal should be at least about 5
ppm and not more than about 200 ppm, based on the weight of the oil
being treated.
A level of about 10-50 ppm ruthenium is preferred and a level of
about 10-20 ppm is most preferred. On the other hand, the level of
acid should be not more than about 4 percent by weight, based on
the weight of the oil being treated, with the lower end being
determined on a case-by-case basis. The preferred level of acid
will be about 0.8 to 2.4 percent by weight.
Finally, the reaction should be carried out in the absence of any
significant amounts of oxygen. Thus, common vegetable oils such as
linseed oil may, in accordance with the invention, be conjugated
efficiently and economically to produce modified oils having unique
drying properties.
The criteria for the oil substrate is that a significant amount of
unsaturated fatty acid triglycerides (such as linolenic, linoleic,
eicosapentanoic, etc.) are present which have conjugatable double
bonds. This oil is then conjugated by using any of several methods
which may be chosen based on an optimization of yield and
production costs for the conversion. In general, the production
costs result from the catalyst used, oil pretreatment reaction
temperature, time and pressure required in the press, and the like.
Some examples of the inventive methods of conjugation are described
in the above-identified companion application, and are based on a
use of one or more of the following catalysts: ruthenium, SO.sub.2,
amine hydroiodides, primary alcohols, alkali, anthraquinone,
nickel/carbon, and others.
Examples of useful ruthenium complexes are dodecacarbonyl
triruthenium, dichlorotris(triphenylphosphene) ruthenium (II) and
ruthenium (III) 2,4-pentanedionate. An example of a useful
ruthenium salt is ruthenium (III) chloride hydrate which is
particularly preferred in the practice of this invention. An
example of a covalent compound is ruthenium dioxide.
Optimally, it has been found for dodecacarbonyl triruthenium, a 50
ppm ruthenium basis amount of catalyst converted linseed oil to 75%
conjugated linolenic acid and 25% conjugated linoleic acid product
with a reaction temperature of 180.degree. C. and a reaction time
of 1 hour. With the triphenylphosphene, reaction of the methylene
interrupted double bonds had somewhat increased selectivity forming
a greater proportion of trans isomers prior to proceeding to
conjugation. It was intensely active, producing 85.3% conjugation
of linolenic acid in three hours with 10 ppm ruthenium basis and
180.degree.. The pentanedionate gave a conjugation of 50.7% at 20
ppm and 180.degree. C.
It has been found in nearly all cases that when most forms of
ruthenium are allowed to come into contact with the substrate under
the reaction conditions, they will solubilize into the substrate as
homogeneous catalysts or be converted into homogeneous catalysts.
Solubilization and activation of the ruthenium is achieved
optimally with the use of formic acid. The greatest success is
achieved by the presentation of ruthenium to the substrate (linseed
oil or organic compound) in a monomolecular form. Most
organoruthenium complexes are soluble in the substrate allowing the
dispersal of ruthenium in molecular form. The ruthenium, so
dissolved, can then be further reacted and activated into highly
active catalysts by formic acid and other acids and alcohols, as
discussed above. The action of the formic acid is not fully
understood at this time. It may act to reduce the ruthenium complex
into dispersed metallic molecular ruthenium.
It is preferred in the practice of the invention to use ruthenium
(III) chloride hydrate. This compound is preferred not only because
of cost and availability, but also because no costly conversion to
an organo-ruthenium complex is required. As an example, RuCl.sub.3
-hydrate may be solubilized into linseed oil by prior
solubilization into alcohols or organic acids such as methanol,
ethanol or formic acid. The resulting RuCl.sub.3 solution can then
be dispersed and eventually completely dissolved into solution. For
example, only 20 ppm of ruthenium as RuCl.sub.3 -hydrate was found
to be needed to produce a conjugation of 85% of linseed oil.
The conjugated triglyceride product may then be blended with a
triglyceride such as one which has been hardened by hydrogenation
to produce a very hard fat with a high melting point; examples of
which would be soy stearin, cotton seed stearin, and palm oil
stearin. A high melting point hydrocarbon wax may also be used as a
blending agent. One preferred example of a high melting hydrocarbon
is a petroleum byproduct known as petroleum based slack wax or
emulsion waxes. The hard fat and wax with a high melting point are
almost equally effective. The choice of which to use depends
largely upon cost and possible detrimental disadvantages such as
increased volatility, etc.
The method used to apply the co-adhesive material onto the strands
may employ a spinning disc, air atomization, spray, or the like,
depending primarily upon the form of the adhesive material,
available equipment in the mill, and the end use application. A
solid form of the inventive co-adhesive material and wax could be
used in the manner that slack waxes are used. An emission or
suspension may be used by mills that are currently using a wax
emulsion. A straight conjugated triglyceride oil solution could be
supplied to mills as a co-adhesive that is premixed or mixed in
line with the PF, UF, or isocyanate adhesive component. If they
wish to do so, these mills may still use a petroleum based wax as a
sizing agent.
The total processing time and pressure varies with the parameters
of a given mat. The following is an example of the noted press
conditions for a commonly used mat. These conditions may vary for
other mats. For example, thicker mats may require longer press
times and greater pressures.
Wood chips or another agriculture based composite material and the
adhesive are blended in a blender rotating at 20-24 RPM. The
adhesive is applied via a coil spinning disc atomizer operating in
the range of approximately 10,000 to 14,000 RPM. The panel is
pressed in a hot press heated to about 380.degree. F. and closed to
apply a pressure of about 525 PSI until a desire sistance is
reached. At approximately 1 minute, pressure is reduced to holding
pressure to "cook" the adhesive. At about 4.5 minutes, the press
pressure is reduced to 0 PSI to degas the panel. The press is
opened at about 5 minutes after it was closed.
The blended product enables an optimal incorporation of the
adhesive system onto the wood fiber substrate which is to be bonded
and produces the best overall combination of wood panel properties
needed in these applications. These wood panel properties include
internal bonding, edge swell, pH, modulus of rupture ("MOR") and
modulus of elasticity ("MOE").
Since the conjugated triglyceride adhesive works in conjunction
with almost all co-adhesives with nearly equal effectiveness, it
acts independently of the chemical bonding of each different
co-adhesive. For example, phenolic resins react with excess
formaldehyde in a condensation reaction which polymerizes the
molecules. On the other hand, the adhesive properties of the
isocyanates are based on the reactivity of the NCO groups taking
the form of urethane bridges with the hydroxyl groups of the
cellulose of the wood.
It is theorized that an important additional advantage imparted by
the present overall adhesive system is that it soaks into and
penetrates the surface of agriculture based composites, such as a
wood surface, for example. Thus, when the overall adhesive system
polymerizes, it provides a greater depth of adhesion with a more
thorough coating of the wood surface than would otherwise be
afforded by the use of the resin co-adhesive alone.
A resin, or similar co-adhesive, is needed for making an initial
and rapid bonding of the wood fibers in order to allow the
triglyceride polymerization to continue bonding over a longer
period of time. More particularly, conjugated oils, such as tung
oil, and various bodied and boiled linseed oils have been used for
their strength through oxidative polymerization in protective
paints and coatings for wood surfaces. However, this form of
oxidative polymerization requires longer lengths of time which are
longer than used for wood bonding applications. Therefore, use of a
fast acting co-adhesive is required.
The inventive adhesive system has many advantages. The product has
reduced VOC's since a triglyceride oil blend has no VOC's. The
amount of VOC's produced in the adhesive system is reduced by the
proportion of the blend that is a triglyceride in the formulation
as compared with the proportion which is the phenolic or other
resin co-adhesive. Also, the addition of triglyceride to the
formulation reduces the total amount of adhesive that is required
to make the end product due to an apparent co-adhesive effect.
Thus, production can be increased, especially where a regulation
limits the allowed amount of VOC's. Also, the use of triglycerides
facilitates an increased production without increasing the risk of
stack fires. Another benefit of the triglyceride adhesive system is
the added water protection since modified linseed, tung and other
oils tend to be water repellant. This reduction in water allows
higher moisture content strands to be used. Finally, the
triglyceride portion of the formulation has the advantage of being
a renewable resource product.
GENERAL EXAMPLE
The invention provides bonding which meets or exceeds property
standards for oriented strand board established by the "ANSI"
standards for mat-formed particle board. Some properties which are
important to the wood adhesive industry are: Density, Edge Swell,
Modulus of Rupture ("MOR"), Modulus of Elasticity ("MOE").
A conjugated triglyceride oil is used as a co-adhesive in
combination with a resin or adhesive for wood and wood chip
applications including formed products, oriented strand board
("OSB"), particle board, plywood, and blended composites,
especially those using chips. The adhesive system may also be used
in the manufacture of floor coverings such as linoleum and the
like. A portion of the bonded product may include used plastics,
paper, cardboard, and other virgin or recycled materials.
The conjugated triglyceride should have a conjugation in the range
of 5 to 100% of the portion that is conjugatable, more preferably
50-100%, and most preferably 70-80%, with a high melting saturated
triglyceride optionally added in a range from 2 to 95% of the total
of oil and triglycerides present. It is preferred to use 20 to 35%
high melting saturated triglycerides. In the alternative, the
conjugated triglyceride may be formulated with a high melting
hydrocarbon in a range from 2 to 95%. The preferred range is from
25 to 30%. The high melting compound and the conjugated
triglycerides may be added to the chips, in any order. The adhesive
system may be further modified by chemically introducing additional
functionality compatible with current adhesive systems. This
addition may be in the range from 2 to 95%.
The conjugated triglyceride may additionally be blended from 1 to
100% with heat bodied or blown triglyceride oils of varying
viscosities.
Archer's conjugated triglyceride (a product of Archer Daniels
Midland Company) is preferably mixed with the coadhesive before
applying to the wood chips for optimal mechanical and physical
properties.
The co-adhesive may be taken from the following group:
Urea-Formaldehyde
Phenol-Formaldehyde
Melamine-Urea-Formaldehyde
Polyvinyl Acetate
Isocyanates
Resorcinol-Phenol-Formaldehyde
Protein
Tannin-Formaldehyde
Sulfite-Liquor
One experimental production run produced the following results:
A. Materials used:
1) Aspen Wood Strands
2) Hercules 2100 P wax emulsion, from Hercules Corp. Minneapolis,
Minn.
3) Dyno 2461 Phenolic Resin, from Dyno Polymers, Virginia,
Minn.
4) Isocyanate Resin: MDI (Monomeric Diisocyanate)
B. Press Conditions:
1) 400 degrees F platens metal pads
2) 500 PSI press
3) 30/60 seconds to close press to stops
4) 175-200 PSI 30 seconds (holding pressure)
5) 175 PSI 21/2-3 minutes
6) 1.5 minutes of degas
C. Procedure Used:
1) Blender
Nest line blender rotating at 20 RPM
70 lbs of wood chips
Resin and wax added via a coil spinning disc atomizer at 12,000
RPM, ambient temperature.
2) Orienter
Chips oriented 50/50 face to core layer with a lab scale orienter.
Target density for panel is 40 lbs. Panel size is 24.times.241/2
inch thick.
3) Press
380 degrees F.
525 PSI starting pressure
175 PSI 1.5 minutes
100 PSI 4.5 minutes
0 PSI 5.0 minutes
open press 5.5 minutes
4) Hot Stack 24 hours.
D. Results:
1) Density
2) Edge Swell
3) MOR
4) MOE
The invention adds a second co-adhesive to the fast setting
co-adhesive, resin or glue-like material. In this example, the fast
setting co-adhesive is the PF and MDI. The second material is slow
setting and based upon triglycerides which have a slower set up and
polymerizing time. This combination of fast and slow set up times
enables the fast acting co-adhesive to react at a quicker press
time with a higher moisture strand. The slower reacting resins or
glue-like co-adhesives take longer press times but are generally
less expensive and more readily available to the market. The slower
set up resins are more greatly aided by this invention. The
inventive combination of adhesives which both quickly bonds and
more slowly penetrates, lead to a much stronger bond than was
available heretofore.
The co-adhesive agent is a drying oil which produces additional
bonding strength than most present bonding systems. When this
adhesive system is used, the internal bond strength within a
composite panel is very significantly increased while improving or
retaining at least some other important aspects of conventional
composite panel characteristics, such as moisture tolerance, edge
swell, etc.
This improved adhesive system enables at least a partial
replacement of currently used adhesives and a reduction in the
total amount of adhesives and co-adhesives that are required. Also,
this improved system may be used to produce products of an improved
quality.
Those who are skilled in the art will readily perceive how to
modify the invention. Therefore, the appended claims are to be
construed to cover all equivalent structures which fall within the
true scope and spirit of the invention.
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